External Crystal Selection

[nirmal@nordic]

I am using external Crystal for my custom chip using nrf 51422 controller.... Just wanted to confirm is my setup for the external crystal (16 Mhz) is correct... It is connected between XC1 and XC2

and in my code I am initializing it with

Softdevice_handler_init(NRF_CLOCK_LFCLK_SYNTH_250_PPM, NULL)

It that ok ?? Or I am not configuring external crystal correctly????

thank you....

[FormerMember]

You don't need to initialize the external 16 MHz crystal, as long as the crystal is within the specifications in the nRF51422 Product Specification, chapter 8.1.2, you are fine.

The crystal selection in SOFTDEVICE_HANDLER_INIT(..) is for the low frequency clock (32.768 kHz), and you have three options:

• Use external LFCLK crystal
• Use internal synthesized oscillator
• Use internal RC oscillator

The recommended choice is to use an external LFCLK crystal or the internal RC oscillator. The reason is that the synthesized oscillator uses considerably more current, see the nRF51422 Product Specification, chapter 8.1.7.